The present disclosure relates generally to three-dimensional (3D) imaging and, more particularly, to methods and systems that facilitate suppressing photon crosstalk between individual pixels of an avalanche photodiode detector array.
Over time, continued operation of a component with one or more defects may reduce performance of the component, and/or lead to component failures. Accordingly, at least some objects are inspected to determine a size and/or shape of all, or a portion, of the object and/or to detect defects that may be present in the object. For example, known gas turbine engine components, such as turbine or compressor blades, are routinely inspected to detect fatigue cracks that may be caused by vibratory, mechanical, and/or thermal stresses induced to the engine. Moreover, some gas turbine engine blades are also inspected to detect deformations, such as platform orientation, contour cross-section, bow and twist along a stacking axis, thickness, and/or chord length, at given cross-sections of the object. Generally, detecting defects within components, as early as possible, facilitates increasing the performance of the system in which the component is incorporated and/or reducing component failures.
One known system for detecting component defects is a laser detection and ranging (LADAR) system. Known LADAR systems may also be used for aerial mapping, surveillance, reconnaissance, and/or target tracking. The LADAR system projects a laser beam onto a surface of a target to enable a 3D image of the surface to be generated. An array of photodiode detectors receive light reflected from the surface of the target, and a series of amplifiers and a processor record the positions and corresponding travel time of light detected by each of the photodiode detectors. From this information, the processor develops a 3D image of the surface of the target.
Known LADAR systems can operate in the short wavelength infrared (SWIR) region to enable a target to be precisely identified under low-light-level conditions. An avalanche photodiode (APD) focal plane array (FPA) is one example of a LADAR system that is capable of single-photon level detection and imaging. In order to achieve a high sensitivity to incident photons, the APD pixels of known LADAR systems are biased close to, or even beyond, a nominal breakdown voltage. With such an electric field, a single carrier injected into a depleted multiplication layer of the APD pixel may trigger an avalanche breakdown, producing electrons and/or holes, resulting in an avalanche current. With many photo-generated carriers in the multiplication layer, a secondary photon emission may be generated and undesirably captured by other biased pixels in the array.